Electrically-heated furnace or leer



1 1,515,511. E. E. MIL,NER

ELECTRICALLY HEATED FURNACE OR LEER Filed Feb. i, 1922 5 Sheets-Sheet 1NOV- 924,

FA b INVENTOR Nov. 1924. 1.515511 E. E. MILNER -ELECTRICALL1 HEATEDFURNACE OR LEER Filed Feb. 1, 1922 5 SheetaF-Shoef. 3 1 4.

29'; 29 4 21 22 5 V 1 I ['1 I! 1' l mu u u Iil I g INVENTOR Nair. l

E. E. MILNER ELECTRICALLY HEATED FURNACE 0R LEER 5 Sheets-Sheet 4 FiledFeb. 1

INVENTQR I flunk a E. E'." MILNER ELBCTRICALLY HEATED FURNACE on LEERFiled Feb 1, 1922 s Sheets-Sheet 5 5M i? flwm 4 7 1 WW Patented Nov. 11,1924. a UNITED STATES PATENT OFFICE.

EDWIN E. MILNER, OF SCOTT TOWNSHIP, ALLEGHENY COUNTY, PENNSYLVANIA, AS-SIGNOB TO B. L. DIXON COMPANY, OF CARNEGIE, PENNSYLVANIA, A CORPORA-Q'Figure 3 1s a plan view TION OF PENNSYLVANIA.

ELECTRICALLY-HEATED FURNACE OB LEEB.

Application filed February 1, 1922. Serial in). 533,484.

To all whom it may concern:

Be it known that I, EDWIN E. MILNER, a citizen of the United States,residing in Scott Township, in the county of Allegheny, State ofPennsylvania, have invented a new and useful Improvement in ElectricallyHeated Furnaces or Leers, of which the following is a full, clear, andexact description.

My invention relates to furnaces or leers and "articularly to suchfurnaces or leers which are heated by electricity.

Heretofore attempts have been made to electrically heat furnaces orleers but such attempts have been unsuccessful commercially because ofcost of installation and ineflicient heating.

I have devised means whereby the cost of the equipment is not abnormaland by which the energy supplied thereto is eflicientl transformed andthe heating chamher 0 the furnace or leer is properly heated. Means arealso provided by which the temperature may be controlled so as toproduce suitable zones or regions in the heating chamber when such zonesor regions are necessary as, for instance, in annealing leers fortreatment of glass ware.

By the use of electric heat the expensive muffle construction is avoidedwhen the furnace or leer is to be used in the treatment of lass ware orother articles which might be damaged by products of combustion.

I have used an annealing leer. to illustrate a furnace structureembodying my invention, but my invention is not limited to leers as theprinciples of my invention may be used in many kinds of structures.

My invention will be better understood by reading the followingdescription taken in connection with the accompanying drawings forming apart thereof and in which,

Figure 1 is a longitudinal vertical section of an annealing leerembodying my invention;

Figure 2 is a cross-section .on the line II-II of Figure 1; 7

shown in Figure 1; a

Figure 4 is a longitudinal vertical section of a part of a leer showinga modified form of my invention;

Figure 5 is a cross-section of one-half of the leer of Figure 4 on lineV-V;

Figure 6 is a vertical longitudinal section of the device j of the leershowing a further modification of my invention;

Figure 7 is a cross-section of one-half a leer shown in Figure 6 on lineVIIVII; Figure 8 is a cross-section of a leer similar in construction tothat shown in Figure 1, but having the heating units arrangedlongitudinally of the heating chamber;

Figure 9 shows a detail of construction of a reflectorand its locationin the leer. This view is on a larger scale than the. other vlews; l

Figure 10 shows a diagram of the electrical circuits for the type ofleer shown in Figures 1 to 8 inclusive;

Figure 11 shows .a diagram of electrical circuits of the leer as shownin Figure 8;

Figure 12 shows a detail of the supporting means for the heatin units.

Referring to the rawings, the numeral 1 designates the heating chamber.The walls of this chamber may be of any suitable andstandard'construction. The side walls may be made of the brick 2, on theoutside of which is placed a wall 3 of insulating material, such askieselguhr brick or any other similar material. The roof wall of thechamberis made up of a series of reflectors 4. The reflectors may takeany desired form, but those represented in the drawings are parabolicfor reasons which will be given later. The reflectors 4 extendtransversely across the roof of the heating chamber as shown in Figure 1and are supported in position by key blocks 5 having the general shapeof I-beams. The key blocks 5 are provided at their lower ends withflanges 6 against which the edges of the reflectors 4 rest, as shown indetail in Figure 9. The key blocks 5 are provided at their ends withvertical recesses 7 as shown in Figure 1. Hanger bolts 8 pass throughthese recesses and support the key blocks in place. The hanger bolts aresupported by transverse channels 9 which pass over the outside of .theroof of the heating chamber. From the foregoing, it will be evident thatthe reflectors are supported in position by the frame work of the heatinchamber.

As will be noted rom Figure 1 the reflectors are curved so that acorrugated or reentrant surface is produced by the reflectors along theroof of the the heating chamber. The top of the roof is leveledbyfilling ico in with a powder or sand 10 as shown in Figure 1. Asuitable material for this is kieselguhr. This material forms a goodin-- sulator on the back of the reflectors. On top of the material 10are placed insulating brick 11, such as kieselguhr brick or other.suitable material.

The side walls of the heating chamber are held together by the usualside buck sta s '13 and tie rods 14. The end walls are he (1 together inthe usual manner by the buck stays 15 and tie rods16. Longitudinalmembers 17 are connected to the supporting channels 9 so as tostrengthen the frame structure.

The front wall of the heating chamber may be constructed or any suitablematerial such as fire brick. This front wall is provided with one ormore openings 18 through which the material to be annealed or otherwisetreated is introduced to the heating chamber. These openings areprovided with anysuitable closure 19. The heating chamber is providedwith any desired type of conveyor 20 for the well known purpose ofconveying the material through the leer.

That portion of the heating chamber underneath the conveyor may beconstructed of any desired material usually used in the construction ofleers. In Figure 1 this construction is of fire brick 21 having achamber therein filled with insulating material 22, such as kieselguhr.

Connecting with the heating chamber 1 is a tunnel 23. The tunnel 23 maybe of any suitable length and construction desired. The tunnel 23 isprovided with insulating layers 24, the number of which decreases in thedirection away from the heating chamher. The decreasing of the thicknessof the insulating material allows the tunnel to become cooler and thematerial is therefore gradually cooled as it is moved away from theheating chamber. This construction and action are well known to thoseskilled in the art.

The chamber 1 is heated by a series of electrical heating units 25, 26and 27 which are arranged in the roof wall of the heatin chamber, one ofsaid units being supports in operative relation to each of thereflectors 4. In the construction shown in Figure 1 a heating unit 28 isprovided in the front wall and four heating units 29 are provided in thebase of the heating chamber underneath the conveyor. A covering 29 ofsilicon carbide tile is placed over the units 29 to protect the unitsfrom bits of glass that might fall thereon from the conveyor 20. Thesetiles are ood heat conductors. In the structure of Figure l the heatingelements do not extend down the side walls of the chamber but extendonly across the roof, end wall and base of the chamber. The heatingunits are made up of non-conductor core 30 shown in detail in Figures 9and 12 around which is wrapped or coiled a resistance wire 31 of anysuitable material. The units are supported b the arrangement shown inFigure 12. This construction comprises a sleeve 32 which has an openinginto which reduced end portions 33 of the adjacent cores 30 enter. Thesleeve is provided with an extension 34 which passes through thereflector 4 and is held in place by a Washer 35 and nut 36. Any othersuitable means may be used for supporting the heating units in place.The cores 30 may be of any desired length. A spacing member 37 surroundsthe projection 34 and accurately spaces the sleeve 32 from the face ofthe reflector.

Figures 4 and 5 illustrate a modification of the invention differingfrom the construction of Figures 1 and 2 in that the heating units 25,26 and 27 extend across the roof of the heating chamber and down thesides thereof. There is only one of the units 29 in the base of theheating chamber, whereas there are four in the construction of Figure 1.

The construction shown in Figures 6 and 7 differs slightly from thosepreviously described in that this construction is provided with aheating unit 38 which extendslongitudinally of the heatin chamber alongthe side walls near the roo Figure 8 shows a still farther modificationin which heating units 39 extend longitudinally of the heating chamberin the roof. This construction also has a heating unit 29 in the samerelative position as the constructions heretofore de scribed.

Figures 10 and 11 illustrate diagrammatically the circuits of theheating units. The units are supplied from any suitable source ofelectrical energy, such as the generator 40. The unit 25 has anadjustable rheostat 41 in series therewith and is also provided with aswitch 42.

The units 26 are connected in parallel between the busses 43 and 44.These three units have an adjustable rheostat 45 in series therewith andthey are each provided with a switch 46.

Each of the units 27 is provided with an adjustable rheostat 47 and alsowith a switch 48.

The purpose of the foregoing arrangement of electrical circuits is topermit of accurate control of the temperature inside the heatingchamber. By reason of the arrangement illustrated any one'of the unitsmay be cut out of operation by opening the corresponding switch. Theheat generated by any particular unit may also be varied by the properadjustment of the rheostats in series with the units. The arrangement issuch that the chamber 1 may be divided into zones or regions of varyingtemperature as is necessary in some instances in the treatment ofvarious articles.

Figure 11 illustrates one unit used in the type of furnace shown in-Figure:8, that is to say, wherein the units extend longitudinally inthe roof of the heating chambr. The units are so wound with the resistance wire as to generate moreheat per unit of length in someportionsthereofthan in others. The portion 49 has the greatest number of turnsthereon and therefore generates a greater heat for a given length thanthe portion 50. The portion 50 generates I more heat per unit of lengththan does the portion 51 and the portion 51 likewise generates more heatper unit of length than does the portion 52. That is to say, theresistance wire is wound closer and closer together throughout thelength of the unit from right to left as viewed in Figure 11. Connectedto the'resistance wire are leads 53 and 54. These leads are'connectedtogether by a wirefl55 in which is placed an adjustable resistance 56.These wires and leads constitute a shunt around the portion 49 of theunit. By varying the resistance 56, any desired amount of energy may beshunted around the portion 49 so as to con- I trolits temperature. Theshunt circuit may be opened by moving the inter-off of the resistance,thus allowing al 'of the current to pass through the portion 49.

The portions 50, 51 and 52 are likewise provided with adjustable shuntresistances 57, 58 and 59, respectively, so that the temperature ofthose portions may be likewise controlled by controlling the amount ofresistance in shunt therewith. Each of the units is provided with theseregulating means so that they may be individually or collectivelyregulated so as to produce zones or regions differing in temperatures inthe heating chamber. of the leer. The source of current is connected atthe points marked plus and minus on Fi re 11.

In order that the heat which is emltted by the heating units may be moreefficiently applied to the heating chamber, the surface of thereflectors indicatedby the heavy line 60 of Fig.9 may be glazed by anydesired method or this surface may be painted or coated or otherwisetreated so that it will act as a more eflicientreflector than would bethe case if that surface were dull. The full lines 61 in Figure 9illustrate the lines of direct radiation of heat. from the resistancecoils in all directions and the dotted lines 62 illustrate the reflectedrays coming from the reflector. By reason of the parabolic form of thereflector surface it Will be noted that the reflected lines 62 areparallel with each' other, whereas the lines of direct radiation radiatein all directions from the heating unit.- Any desired form or shape maybe given to the reflect- .ing surface and the reflectors may be made ofany suitable material. Due to the high temperature employed, howeyer, itwill be necessary that the these reflectors be constructed of materialcapable of Withstanding the temperatures and any material may thereforebe used which will meet this requirement.

My invention has many advantages; among which may be mentioned that theheating units are simple in construction and are placed entirely withinthe heating cham r so that fullefi'ect is given to the heat radiatedtherefrom; the units are inset in the walls of the heating chamber sothat they are protected by the ridges produced by the lower ends of thekey blocks 5; the inset portionsxwhich receive the units act asreflectors so that the heat emitted from the units is eflicientlyreflected into the heating chamber; the heating chamber is free fromproducts. of combustion and drafts caused by such combustion; all theadvantages of a 'Inuflle leeror furnace are secured with a constructionwhich is much less expensive; means are provided for controlling thetemperature of the heatingchamber so as to divide the same into zones orregions of different temperatures; heating units are provided in thebase and front Wall of the heating chamber to preheat the conveyorbefore the articles are placed thereon; by reason of 'the simpleconstruction of the heating units and the walls of the heating chamber,the construction of the leer is simplified andthe cost thereof muchreduced; by reason of theprovision of reflecting surfaces in the Wallsof the heating chamber, thereis less tendency through the walls. will beapparent to I claim: I

1. In an electric furnace, the combination of a chamber to be heated, aplurality of electrical heating elementsiin said chamber, reentrant heatreflecting surfaces in the Many other advantages those skilled in theart.

for the escape of heat Cal walls of said chamber, means for support- .7

ing one of said elements in each of said reentrant surfaces in spacedrelation thereto to permit free radiation of heat from substantially theentire area of each surface, and

means for varying the effective heat in zones either transversely-orlongitudinally of the,

furnace, substantially as described.

2. In an electric furnace, the combination of a chamberto be heated, aplurality of.

heat reflectors forming a part of at least one 6 means-for varyingthesaid chamber, and an electric heating element supported in operativerelation to each of sald reflecting surfaces, substantially as de-'scribed.

- 5. In an electric furnace, the combination of a chamber to be heated,a plurality of inset heat reflectors arranged in continuous side-by-siderelationship and constituting partof the wall of said chambenand aheating element for; each of said reflectors, substantially asdescribed.

6. In an electric furnace, the combination of a chamber to be heated, aplurality of removable reflectors inset in the wall of said chamber andadapted to freely directheat rays into the chamber and aheatin-g'element for each of saidireflectors, substantially asdescribed. y

7 In an electric furnace, the combination of a chamber to be heated,reflectors therein, an electric heating unit supported in heatradiatingposition in each of said reflectors,

means regulating the generation of heat by said units, afurnace frame,and means su porting saidrefle'ctors directly from said frame,substantially as described. 8. In an electric furnace, the combinationof a chamber to be heated and a plurality of electric heating unitssupported in heat radiating offset portions of the walls of saidchamber, and means regulating the 'generation of heat in said units toproduce zones of varying temperature in said chamber, substantially asdescribed,

9. In an electric furnace, the combination of a chamber to be heated, apluralit of electric heating units supported in 0 set" portions of thewalls of said chamber, a conveyor in .said chamber, and an independentelectrical heating unit in the bottom of said chamber below theconveyor, substantially as described.

10. In an electric furnace, a to wall having a series ofkey block's,heat re ectors supported by said blocks and a heati ng element in eachof said reflectors,-substantia1ly as described; I 11. In an electric.furnace, a top wall havmg a series of transversely extending key blocks,transversely extending "heat reflectors supported by said key blocks,and a heating element in each of said reflectors,

substantially as described.

12. In an electric furnace, a top wall havmg a series of key blocks,heat reflectors supported by said key blocks, a heating element in eachof said reflectors, an' endless conveyor in said furnace, and anelectric heating means for heating the lower'run of said conveyor,substantially as described. 13. In an electric furnace, a to wall havmga serles of key blocks, heat re ectors supported by said key blo ks, aheating element in each of said reflectors, and means for reg.- ulatingthe heat generated in said elements, substantially as described.

.In testimony wherof I have hereunto set my hand.

EDWIN E. MILNER.

. Certificate of Correction.

It is hereby Count Pennsyl vania,

[SEAL.]

certified that in Letters Patent No. 1,515,511, 1924, upon theapplication .of Edwin E. lihliier, of Scott for an m aovemeit greqLeers, errors appear in. the-print specl ca on 1 u iemacnhg Page 4,lines 7 and 8, claim 4, strike out zvgi'gsmfafier the word of insert thesaid Letters that'the same may conform, to

this 26th day of May,

anted November 11, flownship, Allegheny Electrically-Heated- Furnaces orcorrection as follows: of said chambers and Patent should be read withthese 7 the record of the case in the .KARL FENNING, Acting Commissioner0; Patents.

